Macrophomina phaseolina was isolated from the roots of symptomless plants of 23 weed species found in Australian mungbean fields. Eight of these species are new host records for the world while 14 of the remaining 15 species are new reports in Australia. Isolates of M. phaseolina from all weeds were pathogenic on mungbean seedlings. These results suggest that apparently healthy weeds infected by M. phaseolina may serve as alternative hosts of the pathogen in Australian grain production regions.